The most used printing form in rotary offset printing machines is a pre-coated aluminum plate. Its biggest advantage is simplicity and speed in manufacture. Also substantially used are multi-metal plates, mostly formed of three metals, to constitute tri-metal plates. Usually, either aluminum or sheet steel is used as the carrier substrate metal. These types of plates are used particularly for printing with high numbers of printed runs, and where high stress resistance and long life is important. The excellent surface characteristics of these plates can be enhanced, even, by additionally anodizing the surfaces.
These printing plates, generally, are circumferentially discontinuous. Opposite edges of the plates, as they are wrapped around a plate cylinder, are formed with holes to engage in register pins of a clamping arrangement located in an axially extending groove of the printing cylinder. The printing form is centered on the engagement pins and hooked into the cylinder groove. Prior to hooking the printing form into the groove, the edge is bent at an angle of about 90.degree.. The trailing end of the plate is also introduced into the cylinder groove, and a clamping arrangement tightly, circumferentially clamps the plate on the cylinder. To attach such a plate to a cylinder requires a groove extending over the entire width of the cylinder and clamping segments which are located within the cylinder groove. The printing forms begin and end in the region of the groove. This interruption in the circumference prevents the formation of endless images and, additionally, causes problems in operation. The cylinder is subjected to vibrations and oscillations due to the groove, and the clamping apparatus therein. This limits the printing speed and the oscillations interfere with best printing quality.